Lynn wrote:But we aren't talking about water balloons here.
It is, however, almost the exact same effect. Just without the being on fire part. In fact, for holy water, it IS exactly the same thing as a water balloon. Unless you've got two targets that are at "hug range" to each other, getting an EFFECTIVE hit on both people simultaneously is going to be rather unlikely (I'd consider it if the throw attack was a natural 20, perhaps, but then I would make it two fully affected targets, and no other splash effect).
For burning oil flasks and/or alchemist's fire type splash weapons, I always felt the Pathfinder version of alchemist's fire pretty accurately covered it:
"A direct hit deals 1d6 points of fire damage. Every creature within 5 feet of the point where the flask hits takes 1 point of fire damage from the splash. On the round following a direct hit, the target takes an additional 1d6 points of damage."
There's a little more rules to it, about how to extinguish the flames before taking the second 1d6, etc, but those are less relevant to LotFP.